1. DEVELOPING ENTERPRISE APPLICATIONS USING EJB
SESSION BEAN

2. CONTENTS Enterprise Java Beans JNDI Logical Architecture of EJB
Session Beans
EJB Development Process
Enterprise Application Development Process
Workshops
Exercises

3. COMPONENT ARCHITECTURE
Components are building blocks of an application
Provides a set of services or functions, such that it can easily interact with other applications or components
Consists mainly of Web components (JSP, Servlet, …), Business components (EJB), and Service components (Mail, JDBC, JMS …).
Flexible, Portability and Reusable
An enterprise application is usually composed of a three-layer architecture
Presentation Layer (Web Component, GUI Component, Client console)
Business Layer (Business Component)
Business logic
Comprises business rules or methods using which specific business functions can be managed
Refers to the workflow or the ordered task of passing data from one software sub-system to another
Business objects
Are the set of objects and the relationships between them
Encapsulate both the data & business behavior associated with the entity that it represents
Have the required features: reusability, access control, remote access, multi-user, highly available, state maintenance, transactional, and shared data
Data Layer
Access control: phan quyen su dung

4. DISTRIBUTED OBJECT ARCHITECTURE
Web Application Server
Request DB
Response

5. EVOLUTION of EJB Building application software is complexity
The software can process multi-data
The software is available online.
The developer worries about the security, transaction, scalability, concurrency, resource management, persistent, error handling, and many more system level problems.
Software assurance and performance are affected because the developer can not concentrate fully on the developing the business logic (from implementation logic).
EJB was developed so that it would:
Specialize in handling the business logic of an application
Be robust
Be secure so that it cannot be tampered.
EJB provides a component to create middleware which is deployed on Application Server (3 tiers architecture).
EJB Component has been designed to encapsulate business logic.
Robust: thiet thuc, manh me, chac chan
Temper: ep lai, co lai – giam tinh nang

6. EJB Released by Sun Microsystems in 1998
EJB is a server-side component that simplifies the process of building enterprise-level & distributed applications in java
Write-once, run-anywhere, middle-tier components which consists of methods that implements the business logic
EJBs are interprocess components and Java Beans are intraprocess components
There are two more ways of looking at EJBs
EJBs are specification: lay out rules and standards on how you should code your EJBs.
EJBs are Java interfaces: EJBs are code by the extending/implementing the EJB interfaces available in the J2EE package
Interprocess: lien tien trinh
Intraprocess: noi xu ly

7. EJB (cont) Characteristics Types
Hides server-side system level issues from developers.
Defines a standard component architecture that enables you to build distributed object-oriented business applications.
Facilitates creating enterprise-level applications by allowing easy integrating with other EJB components as well as with other components, such as servlets, Java Server Pages (JSP), and Java Beans.
Enables you to create components and applications that are reusable across various J2EE-compliant servers
Types
Session Bean – Represents business process without having persistent storage mechanism
Stateless Session Bean
Stateful Session Bean
Entity Bean – Persists across multiple sessions and multiple clients & Having persistence storage mechanism
Bean-managed Persistence [BMP]
Container-managed Persistence [CMP]
Message-driven Bean – Asynchronous messaging between components of EJB.

8. EJB IN J2EE ARCHITECTURE

9. APPLICATION/EJB SERVER
Provides many services
Network connectivity to the container
Instance Passivation – Temporarily swap out a bean from memory storage
Instance Pooling – Multiple clients share same instance
Database Connection Pooling – Contains a set of database connection
Precached Instances – Maintains cache, which contains information about the state of the EJB
Other services
Runtime Environment
Support the containers interaction
Process and Thread Management
Receive and process requests
System Resource Management
Feasible: thuan tien, tien loi

10. EJB CONTAINER
Acts as an interface between an enterprise bean and client
Provides following services
Security
Transaction Management
Persistence
Life Cycle management
Remote Client Connectivity
Responsible for providing several APIs
J2SE API
EJB Standard Extension
JDBC Standard Extension
JNDI Standard Extension
JMS Standard Extension
JavaMail Standard Extension (for Sending mail only)
JAXP (Java API for XML Processing)
JTA Standard Extension (Only UserTransaction interface)
Spawn: de trung, tao ra

11. JAVA NAMING and DIRECTORY INTERFACE
A naming service (which has its own set of rules for creating valid names) allows you finding an object in a system based on the name associated with the object which is called “binding”.
A directory service is an extension of a naming service (an object is also associated with a name, which can be look up, and allowed to have attributes)
Java Naming and Directory Interface (JNDI) is a specification for accessing naming and directory services
Java Naming and Directory Interface provides the naming and directory functionality to Java applications.
Provides a standard interface to locate the components, users, networks, and services placed across the network.
Bridges the gap between directory services and makes it possible for the developer to write portable naming and directory services
JNDI abstracts the code from a dicretory service and allows the user to plug in a different directory services. (without changing the service code)
JNDI provides javax.naming.* interface
JNDI separate two parts
JNDI API
JNDI SPI
Naming Concepts of JNDI
Atomic: It’s a simple and basic name. Ex: Windows
Compound: the collection of one or more atomic names. Ex: C:\Windows\System32
Composite: A name has multiple naming system. Ex̣:

12. JNDI ARCHITECTURE Java Application
Accessor Naming Directory services through APIs
JNDI API
NAMING MANAGER
allows Naming and Directory vendors can plugin transparency
JNDI SPI
DNS
RMI
CORBA
LDAP …
LDAP: Lightweight Directory Access Protocol

13. INITIAL CONTEXT FACTORY
Naming System
Binding
Initial Context Factory is the point where all naming and directory operations are first performed.
When the initial context is acquired, all information pertaining to this must be provided to JNDI.
The internal storage of JNDI emulates tree data structure. Each InitialContext acts like an internal node and each reference to the resources acts like the leaves
The directory context or directory object is another type of context. It is used to define methods for inspecting and modifying attributes associated with a directory object.
Acquire = obtain, get
Pertain: dua toi, gan den

14. <Biến context>.lookup(tên đối tượng)
JNDI API & LIBRARIES
The Context is represented by the javax.naming.Context interface that has the necessary methods to put objects into the naming service, and also to locate them.
The starting point is called an InitialContext, represented by javax.naming.InitialContext interface
The references in JNDI are represented by javax.naming.Reference interface
The lookup() method retrieves the object bound to the name and throws a javax.naming.NamingException, if a naming exception is encountered
<Biến context>.lookup(tên đối tượng)
The remote calls in EJB make use of RMI-IIOP (Remote Method Invocation-Internet Inter-Orb Protocol) which does not support explicit casting of the EJB object obtained from the remote object to a local object. Instead, Java a RMI-IIOP provides a mechanism to narrow the Object you have received from your lookup to the appropriate type by using the javax.rmi.PortableRemoteObject class & its narrow() method
The method narrow() of which parameters narrowFrom is the object that has to be narrowed and narrowTo is the desired type. It returns the object which is cast to the desired type and throws ClassCastException, if narrowFrom cannot be cast to narrowTo
The supported files are jndi.jar, fscontext.jar, providerutil.jar

15. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
Provide the components to solve business problem (that are packaged them to the ejb-jar file
Reusable components
Assemble other components into application.
Distribution

16. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
App Assembler
Create EJB
For Assembling different EJB Components in order to build a complete application
Analyzing a business problem and assembling EJB components accordingly to solve the problem
Building new EJB components
Writing the integration code required to associate the EJB components build by different bean providers

17. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
App Assembler
Deployer
Create EJB
Assemble components
Customizing enterprise bean
Accumulate information about operational requirements such as security, hardware, and transaction before deploying the bean
For deploying an assembled application in an application server

18. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
App Assembler
Deployer
Create EJB
Assemble components
Providing the deployment tools that are required by the deployer for deploying EJB components
Providing run-time support for beans that are deployed on EJB Server
Container Provider

19. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
App Assembler
Deployer
Create EJB
Assemble components
For providing EJB Server, which manages client access to an application in a distributed environment
For managing transactions and distributed objects
Provide Container
Container Provider
Server Provider
Apply

20. PARTIES INVOLVED in EJB DEPLOYMENT
Bean provider
App Assembler
Deployer
Systems Administrator
Create EJB
Assemble components
Deploy components
Managing and running an EJB application
Configuring and managing the network infrastructure of an EJB application
Provide Container
Container Provider
Server Provider
Managing the working of EJB server and EJB container
Apply
Monitoring the working of deployed EJB applications

21. LOGICAL ARCHITECTURE of EJB
EJB container/ server
Create Home Obj Instance
EJB Context
(Local) Home
Object
Client
EJB Obj Reference
Create instance Bean
create DB
Invoke Methods
Send invoke
connect
EJB
Object
Enterprise
Bean
JNDI
Retrieve data
Lookup
Naming
Services
03 tiers Architecture

22. COMPONENTS OF EJB Components of an enterprise bean The Remote
interface
The Local Interface
The Home
Interface
The LocalHome
Interface
The EJB object
The Home object
The EJB-jar file
Deployment
Descriptors
The bean class

23. EJB OBJECT EJB Container/Server (substitute object)Proxy
The container is the middleman between the client and the bean. It manifests itself as a single network-aware object.
This network-aware object is called the EJB Object
EJB Container/Server
Transaction
Security
EJB Obj
Client
Delegates Method
Instance Bean
Request/ Call/ invoke method
Manifest: hien thi, chung to
Delegate: giao thac, uy nhiem
Return values
Pools
(substitute object)Proxy
.....
Bean configuration to use
Management Session
JNDI registry
... 23

24. EJB OBJECT (con’t) Interface javax.ejb.EJBObject
Methods
Descriptions
getEJBHome()
Retrieves the reference to the corresponding Home Object
getPrimaryKey()
Return the PrimaryKey for EJB Object (Entity Bean)
remove()
Destroy EJB Object (delete the bean from the underlying persistent store, means delete a record on DB – Entity Bean)
getHandle()
Obtain the handle (is a persistent reference to the EJB Object) for the EJB Object
isIdentical()
Checks whether two EJB Objects are similar
Relationship between Java RMI and EJB Objects
public interface javax.ejb.EJBObject extends java.rmi.Remote (The physical location of remote object is hidden from the Client RMI)
Can be called from a different JVM
Offers Location Transparency (Portability of Client Code)

25. REMOTE INTERFACE define perform Remote Interface
Functionality of
Implementing in
instance bean
Business
methods
define
perform
Remote Interface
extends java.ejb.EJBObject
public interface Welcome { }
extends javax.ejb.EJBObject
public String welcome()
...
throws java.rmi.RemoteException;
Note: System level operations such as persistence, security and concurrency are not included in remote interface.

26. LOCAL INTERFACE
EJB 2.0 can expose their methods to clients through new Local Interface
Standard Java interface which allows the beans to expose its methods to other bean reside within the same container (local clients)
Eleminate the overhead of the remote method call (java.rmi.RemoteException)
Use pass by reference semantics (speed up in processing and efficiency)
Not inherit from RMI (extends javax.ejb.EJBLocalObject)
public interface WelcomeLocal extends javax.ejb.EJBLocalObject {
public String welcome();
... }
EJB Container/ Server
Session Bean
Other Beans
Invokes
Methods
exposes
Local Clients

27. HOME OBJECT EJB Container/Server
Create new EJB Object
Client
EJB Home
return Object
Create EJB Object
Instance Bean
Return EJB Obj location
EJB Obj
Client code will request for an object from the EJB Object Factory, which know as the home object (instantiates EJB Object)
Responsibilities
Create (Instantiate) EJB Objects
Initial information for EJB Object s
Find or search for existing EJB Objects(Entity Bean)
Remove EJB Objects (deletes the bean from the underlying persistent store)
Select EJB Objects (Entity Bean)

28. HOME OBJECT (con’t)
Interface javax.ejb.EJBHome (extends java.rmi.Remote)
Methods
Descriptions
getEJBMetaData()
Retrieve information about EJB (Beans’ information) that are being worked on. The information received is encapsulated in the EJBMetaData object, which returns the method.
remove()
Destroy EJB Object following
- Passing the javax.ejb.Handle object, which remove EJB Object that is based on the already retrieved EJB Handle
- Passing a primary key to remove beans (one record) from the underlying persistent store.

29. HOME INTERFACE Home Interface public interface WelcomeHome { }
Create EJB Object
Initialize
Home Interface
extends java.ejb.EJBHome
Find, Select
Destroy
public interface WelcomeHome { }
extends java.ejb.EJBHome
public Welcome create()
public Welcome findByPrimaryKey() ...;
...
throws java.rmi.RemoteException;

30. LOCAL HOME INTERFACE
Standard Java interface which allows the beans to expose its methods to other bean reside within the same container (local clients)
Eleminate the overhead of the remote method call (java.rmi.RemoteException)
Use pass by reference semantics (speed up in processing and efficiency)
extends javax.ejb.EJBLocalHome
Notes: LocalObject is used as Return Values
public interface WelcomeLocalHome extends javax.ejb.EJBLocalHome {
public WelcomeLocal create();
public WelcomeLocal findByPrimaryKey();
... }

31. Well-defined interface
BEAN CLASS
Container
Bean
Client
Well-defined interface
communication
Bound
Implements defined method from Component Interface (Remote and Local)
Override default Bean class
These methods are then called by container manage bean and keep the bean informed of important events
EJB can share the propertiess of the serialiable objects because the javax.ejb.EnterpriseBean extends Serializable
Once the interface javax.ejb.EnterpriseBean is implemented, the bean class is confirmed

32. DEPLOYMENT DESCRIPTOR….
<home>Welcomehome</home>
<remote>Welcome</remote>
<ejb-class>Welcomebean</ejb-class> ……
EJB Server/Container
Remote Interface,
Home Interface, Bean ...
The DD points out how the beans must interact with one another
Declare middle ware services requirements of components
The DD supply the bean component and performs the requirements
Life-cycle requirements and bean management: specify how the container should manage the beans
Persistence requirements: inform EJB container whether the bean take care of/ or delegate persistence
Transaction requirements: support transaction
Security management

33. EJB-JAR FILE
Component Interface
EJB-JAR file
(*.jar)
Deployment
Descriptor
Bean class
Create jar file
Home Interface
EJB container decompress, read và extract information contained in the EJB-JAR file.
Generation of the EJB object and the home objects, and the bean. (deployer)

34. SESSION BEANS
A kind of enterprise beans that represent business processes (any task with logic, workflow, and algorithms).
Perform business functions for the clients inside the application server
Represents business process without having persistent storage mechanism
Not permanent in Nature
Are not shareable between clients (only one client can deal with that particular session bean)
Enable a Conversation between a client and the J2EE Server
Life Cycle of a Session Bean
A session bean may last as long as the client session.
Will not survive if the application server changes or crashes.
They are objects which are present in-memory which die along with the surrounding environment and are not persisted in a database.
Types of Session Bean
Stateless Session Bean
Stateful Session Bean
Session bean implement
From javax.ejb.Session Bean
callback methods (invoked on the bean by the container)
business methods
Permanent: khong ben vung

35. CONVERSATION & NON-CONVERSATION
Define as an interaction between a client and a bean.
Is composed of a number of method calls between them
Stretches across a business process with respect to the client.
Stateful session beans can retain their conversational state.
Ex: Shopping Cart
Non-Conversation:
Clear of all previous information (same as the HTTP protocol)
A stateless session bean conducts a conversation that spreads over a single method call.

36. CALLBACK METHODS public void setSessionContext(SessionContext ctx)
public void ejbCreate([args])
public void ejbPassivate()
public void ejbActivate()
public void ejbRemove()

37. EJB SESSION CONTEXT
setSessionContext()
Container
Bean
Associate
Session Context
(Gateway)
Contains information about bean’s status such as reference of bean home interface, client’s security permissions and transactions currently associated with the bean instance.
The EJB session context object enables session beans to interact with EJB container to perform the following functions:
Retrieve the reference to the home objects
Retrieve transaction attributes
Set transaction attributes
javax.ejb.SessionContext interface
setSessionContext()
Comprise: bao gom

38. ejb-jar.xml STRUCTURE <?xml version="1.0"?>
<ejb-jar version="2.1" xmlns="
xmlns:xsi="
xsi:schemaLocation="
<enterprise-beans>
<session>
<ejb-name>Representation Name</ejb-name>
<home>[package.]Home Interface class</home>
<remote>[package.]Remote Interface class</remote>
<ejb-class>[package.]Bean Class</ejb-class>
[<local-home>[package.]Local Home interface class</local-home>]
[<local>[package.]Local interface class</local>]
<session-type>Stateless/Stateful</session-type>
<transaction-type>Bean</transaction-type>
</session>
</enterprise-beans>
</ejb-jar>

39. jboss.xml STRUCTURE
Provides the container information about the JNDI mapping, persistence information and database mapping.
<?xml version="1.0"?>
<!DOCTYPE jboss PUBLIC "-//JBoss//DTD JBOSS 4.0//EN"
"
<jboss>
<enterprise-beans>
<session>
<ejb-name>Representation name</ejb-name>
<jndi-name>name reference to home</jndi-name>
<local-jndi-name>name reference to local home</local-jndi-name>
</session>
</enterprise-beans>
</jboss>

40. STATELESS SESSION BEAN
Is used for a single request conversation
Executes Business operations without maintaining the client state (non-conversation)
Lightweight Component – Doesn’t contains complex data structure
Same Session Bean instance can handle multiple client requests
Improves the scalability of an application
Not having instance variables to store information
Can’t used when information need to be used various method calls
The client has to pass on all the information necessary for the bean through the parameters for the business method.
The client is not responsible for the creation or destruction of the bean
Life cycle
Bean Creation: Stateless are created by the container and added to a bean pool.
Bean Use: Stateless are used when the clients call their business methods.
Bean Removal: Stateless are removed when the EJB container decides there are too many beans in the pool or the beans throw a system exception.
Spawn: de trung, tao ra

41. LIFE CYCLE OF STATELESS
Start
(Does not exist)
Client invoke method
Client called remove()
(or the client times out)
init instance
ejbRemove()
setSessionContext()
ejbCreate()
Instances
(Ready)

42. STATEFUL SESSION BEAN
Is used for business processes that span multiple method request or transactions have to be serviced
Maintains the State of a client
The conversional state must be stored in the bean (Stores client state in instance variable)
Pooling has to be done to conserve resources and enhances scalability.
The container swaps out a bean and saves the conversational state to the hard disk or other storage devices. This process is called passivation.
To passivate a bean a container uses Least Recently Used (LRU) method.
When the client requests for a method, the passivated conversational state is returned to the bean. The bean is again ready to meet the request. This process is called activation.
To activate a bean a container uses Just-in-Time (JIT) method.
Can used when information need to be used various methods calls
Stateful bean instance can service the requests of a single client only
Reduces application scalability

43. LIFE CYCLE OF STATEFUL Client invoke method Start (not exist)
Client called remove()
(or the client times out)
init instance
ejbRemove()
setSessionContext()
Client need more resrc
ejbCreate(arg)
ejbPassivate()
Passivate
Client called method
on passivate
Instances – ready
ejbActivate()
Bean Creation: Statelful are created by the container when a client makes a request for a bean.
Bean Use: Statelful are used when the clients call their business methods.
Bean Passivation: Statelful are passivated or made inactive when the client does not call the session bean business methods for a specified period of time.
Bean Activation: from passivation, the Stateful moves to activation stage when the client request for bean services after a prolonged period of inactivity.
Bean Removal: beans are removed when the container decides there are too many beans in the pool or the beans throw a system exception.

44. ACCESSING from CLIENT SIDE
Possible Clients
Home
Object
JNDI lookup
Ordinary JavaBean
create()
Enterprise JavaBean
EJB
Object
Enterprise JavaBean
JSP Page
Business
Methods
Servlet
Applet

45. [WEB] APPLICATION In EJB
This structure is deployed at JBOSS_HOME\server\default\deploy directory
This structure is name with the extension .ear (include jar and war)

46. EJB DEVELOPMENT PROCESS
Requirement: JBoss GA Application Server
Step 1: Creating a new EJB Module project
Step 2: Creating the new corresponding bean depending on your purpose.
Step 3: Building/ Modifying the business/callback methods on Beans
Step 4: Mapping the JNDI to beans
Step 5: Building the project to jar file
Step 6: Deploying the project on Application server
Step 7: Creating the client application to consume
Step 8: Running the client to test the EJB

47. Step 1: Creating a new EJB Module project
Create new Project
Choose “Enterprise” on “Categories”
Then, choose “EJB Module” on “Projects”. Click Next button

48. Step 1: Creating a new EJB Module project (cont)
Fill your project name
Choose the Jboss Server that is added
Choose the J2EE1.4
Diverging: hướng nào đó
Click Finish button

49. Step 1: Creating a new EJB Module project (cont)

50. Step 2: Creating the new corresponding bean
Choose File menu/ click new File
Choose “Enterprise” on “Categories”
Then, choose “Session Bean” on “File Types”. Click Next button

51. Step 2: Creating the new corresponding bean (cont)
Fill your bean name
Fill or choose the package name
Choose stateless or stateful
Choose remote or local or both
Click Finish button

52. Step 2: Creating the new corresponding bean (cont)
Generate automatically four callback methods:
setSessionContext
ejbActivate
ejbPassivate
ejbRemove

53. Step 3: Building/ Modifying the business/callback methods on Beans
Modifying the callback method if necessary
Adding a new business method
Right click on source code of the Bean file (Ex: CalculateBean)
Then, choose EJB Methods, click Add Business Method…
Fill or type the method name with return type and all parameters
Then, click OK Button

54. Step 3: Building/ Modifying the business/callback methods on Beans (cont)
Cornerstone: important
Implement the body of method corresponding with your purpose

55. Step 3: Building/ Modifying the business/callback methods on Beans (cont)

56. Step 4: Mapping the JNDI to beans
Modify the jboss.xml file as following
Fill your wanted JNDI that you want to reference

57. Step 5 and 6: Building & Deploying

58. Step 7: Creating the client application to consume
Create Java console application
Add reference to EJB project mapping to invoke the remote method on application Server
Right click on library of client project/ click “Add Project …”
Choose the jar file
Modify servlet name
Click Add Project Jar File

59. Step 7: Creating the client application to consume (2)
Adding the code as following (notes: addition the jbossall-client.jar and jnp-client.jar from JBOSS_HOME\client to application project)
Reference to the application server address (location)
Reference to EJB
Invoke the remote interface of EJB on Application Server

60. Step 8: Running the client to test the EJB

61. ENTERPRISE APPLICATION DEVELOPMENT PROCESS
Step 1: Creating a new Enterprise Application project (EJB and Web Client – ear file)
Step 2: Creating the new corresponding bean depending on your purpose.
Step 3: Building/ Modifying the business/callback methods on Beans
Step 4: Mapping the JNDI to beans
Step 5: Creating the GUI to consumes EJB on web modules
Step 6: Building and Deploying Enterprise application on Application Server
Step 7: Executing the Enterprise Application

62. Step 1: Creating a new Enterprise Application project
Choose the Enterprise in Categories
Then, choose the “Enterprise Application” in Projects
Click Next Button

63. Step 1: Creating a new Enterprise Application project
Type the Project name
Choose the Jboss 4.2.2
Choose J2EE 1.4
Don’t change anything that is default by tools
Click Finish Button

64. Step 1: Creating a new Enterprise Application project

65. Step 2: Creating the new corresponding bean Step 3: Building/ Modifying the business/callback methods on Beans Step 4: Mapping the JNDI to beans
Creating stateless bean as whole steps in above tutorials in EJB Development process on the xxx-ejb module

66. Step 5: Creating the GUI to consumes EJB on web modules
Creating the GUI application
Creating the Servlet to process and consume the EJB
Creating the reference to the EJB on the coding by right click on code
Then choose Enterprise Resources, click Call Enterprise Bean

67. Step 5: Creating the GUI to consumes EJB on web modules
Choose the appropriate bean
Modify the Reference Name
Click Ok Button
Modify the Reference Name that is named in jboss.xml at <jndi-name> tag

68. Step 5: Creating the GUI to consumes EJB on web modules
Modifying the code in servlet as following

69. Step 6: Building and Deploying Enterprise application

70. Step 7: Executing the Enterprise Application

71. WORKSHOP ACTIVITIES
Building the EJB with stateless and stateful on Java Sun Application Server

72. WORKSHOP ACTIVITIES (cont)
Building the EJB client to consume EJB Application

73. EXERCISES
Do it again all of demos, workshops, and the following exercises on JBoss Server
Using stateless to write the programs that can do
Building checkLogin() method including 02 parameters username & password using DB
Building the sayHello() method printing Welcome message with the name as the parameter passing to sayHello() method
Using stateful to write the programs that can do
Write a Shopping Cart Program using stateful session bean with some functions as add cart, view cart, and remove cart.
Write a exchange money program